Numerical Simulations of an Oscillating Flow Past an Elliptic Cylinder

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Sid'Ahmed Daoud ◽  
Driss Nehari ◽  
Mohamed Aichouni ◽  
Taieb Nehari
Keyword(s):  
Oscillatory Flow ◽  
Flow Direction ◽  
Elliptic Cylinder ◽  
Longitudinal Force ◽  
Oscillating Flow ◽  
Single Pair ◽  
Vorticity Field ◽  
Flow Around A Cylinder ◽  
Numerical Visualization ◽  
Elliptic Section

This paper presents a numerical investigation of a two-dimensional (2D) oscillatory flow around a cylinder of different elliptic ratios, in order to study the effect of the elliptic form of the cylinder on the vorticity field and the hydrodynamic forces that act on it. The elliptic ratio ε was varied from 1 to 0.1, where the small axis is parallel to the flow direction, simulating cases ranging from a circular cylinder to the case of a cylinder with a profiled elliptic section. The investigations presented here are for Reynolds number Re = 100 and Keulegan number KC = 5. The numerical visualization of the flow for different elliptic ratios shows five different modes of vortex shedding (symmetric and asymmetric pairing of attached vortices, single-pair, double-pair, and chaotic), which depend on the range of the elliptic ratio. The results show that the longitudinal force increases with the reduction of the elliptic ratio. The transverse force appears from the elliptic ratio ε=0.75 and increases with the reduction of this ratio in the range of 0.75≥ε≥0.4, then decreases for ε<0.4. On the other hand, concerning the Morison coefficients the results show that the drag coefficient is sensitive to the swirling layout while the coefficient of inertia does not seem to be much affected by the geometry of the cylinder.

VIV of Flexible Cylinder in Oscillatory Flow

2013 ◽  
Author(s):  
Shixiao Fu ◽  
Jungao Wang ◽  
Rolf Baarholm ◽  
Jie Wu ◽  
C. M. Larsen
Keyword(s):  
Amplitude Modulation ◽  
Wavelet Transformation ◽  
Oscillatory Flow ◽  
Flow Direction ◽  
Cross Flow ◽  
Ocean Basin ◽  
Mode Transition ◽  
Flexible Cylinder ◽  
Modulation Mode ◽  
Lock In

VIV in oscillatory flow is experimentally investigated in the ocean basin. The flexible test cylinder was forced to harmonically oscillate in various combinations of amplitude and period. VIV responses at cross flow direction are investigated using modal decomposition and wavelet transformation. The results show that VIV in oscillatory flow is quite different from that in steady flow; novel features such as ‘intermittent VIV’, amplitude modulation, mode transition are observed. Moreover, a VIV developing process including “Building-Up”, “Lock-In” and “Dying-Out” in oscillatory flow, is further proposed and analyzed.

Liquid-Vapor Oscillating Flow and Heat Transfer in a U-Shaped Minichannel With Internal Wick Structure

2009 ◽  
Author(s):  
Jiajun Xu ◽  
Yuwen Zhang ◽  
H. B. Ma
Keyword(s):  
Heat Transfer ◽  
Oscillatory Flow ◽  
Oscillating Flow ◽  
Transfer Coefficients ◽  
Oscillating Heat Pipe ◽  
Heat Transfer Coefficients ◽  
Evaporation And Condensation ◽  
Flow And Heat Transfer ◽  
Wick Structure ◽  
Liquid Vapor

Liquid-vapor oscillating flow and heat transfer in a vertically placed oscillating heat pipe (OHP) with a sintered particle wick structure inside are analyzed in this paper. The evaporation and condensation heat transfer coefficients are obtained by solving the microfilm evaporation and condensation on the sintered particles. The sensible heat transfer between the liquid slug and the channel wall are obtained by analytical solution or empirical correlations, depending on whether the liquid flow is laminar or turbulent. The effects of the maximum evaporation and condensation angles on the oscillatory flow, as well as sensible and latent heat transfer are analyzed.

An Experimental Study of Heat Transfer of a Porous Channel Subjected to Oscillating Flow

2000 ◽  
Vol 123 (1) ◽  
pp. 162-170 ◽  
Author(s):  
H. L. Fu ◽  
K. C. Leong ◽  
X. Y. Huang ◽  
C. Y. Liu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Surface Temperature ◽  
Steady Flow ◽  
High Speed ◽  
Flow Direction ◽  
Porous Channel ◽  
Oscillating Flow ◽  
Oscillating Flows ◽  
Nusselt Numbers

Experiments have been conducted to study the heat transfer of a porous channel subjected to oscillating flow. The surface temperature distributions for both steady and oscillating flows were measured. The local and length-averaged Nusselt numbers were analyzed. The experimental results revealed that the surface temperature distribution for oscillating flow is more uniform than that for steady flow. Due to the reversing flow direction, there are two thermal entrance regions for oscillating flow. The length-averaged Nusselt number for oscillating flow is higher than that for steady flow. The length-averaged Nusselt number for both steady and oscillating flows increase linearly with a dimensionless grouping parameter k*/kfDe/L1/2Pe*1/2. The porous channel heat sink subjected to oscillating flow can be considered as an effective method for cooling high-speed electronic devices.

Frequency tuning allows flow direction control in microfluidic networks with passive features

Lab on a Chip ◽  
2017 ◽  
Vol 17 (9) ◽  
pp. 1552-1558 ◽  
Author(s):  
Rahil Jain ◽  
Barry Lutz
Keyword(s):  
Frequency Tuning ◽  
Flow Direction ◽  
Oscillating Flow ◽  
Resonance Frequencies ◽  
Microfluidic Networks ◽  
Direction Control ◽  
Parallel Resonance

A bidirectional pump created by rectifying oscillating flow driven at engineered fluidic series and parallel resonance frequencies.

Transverse Vibrations of an Elastically Mounted Cylinder Exposed to an Oscillating Flow

1988 ◽  
Vol 110 (4) ◽  
pp. 387-394 ◽  
Author(s):  
B. M. Sumer ◽  
J. Fredso̸e
Keyword(s):  
Oscillatory Flow ◽  
Oscillating Flow ◽  
Response Patterns ◽  
Test Program ◽  
Current Case ◽  
Number Range ◽  
Response Characteristics ◽  
Vibrational Response ◽  
Transverse Vibrations ◽  
Steady Current

This study reports the results of an experimental work carried out with an elastically mounted rigid cylinder exposed to an oscillating flow. To facilitate comparison, the steady current case is included in the test program as well. The oscillatory flow as well as the steady current conditions are created by the so-called carriage technique. The present study covers the Keulegan-Carpenter number range 5 ≤ KC ≤ 100. The range of the reduced velocity is from 0 to approximately 16 in most of the cases. The tests have been conducted for different combinations of spring stiffness and mass of cylinder. The present results shed considerable light into the understanding of the various vibrational response patterns obtained for different ranges of KC number. The response characteristics of the cylinder have been shown to vary extensively, depending on Keulegan-Carpenter number as well as on the reduced velocity.

A study of forces, circulation and vortex patterns around a circular cylinder in oscillating flow

1988 ◽  
Vol 196 ◽  
pp. 467-494 ◽  
Author(s):  
E. D. Obasaju ◽  
P. W. Bearman ◽  
J. M. R. Graham
Keyword(s):  
Circular Cylinder ◽  
Steady Flow ◽  
Correlation Length ◽  
Vortex Shedding ◽  
Oscillatory Flow ◽  
Transverse Force ◽  
Vortex Street ◽  
Oscillating Flow ◽  
Time Histories ◽  
Vortex Patterns

Measurements of sectional and total forces and the spanwise correlation of vortex shedding are presented for a circular cylinder in planar oscillatory flow at Keulegan-Carpenter numbers, KC, in the range from about 4 to 55. The viscous parameter β is in the range from around 100 to 1665. Circulation measurements around a circuit close to and enclosing the cylinder, are also presented. A mode-averaging technique was used for both sectional forces and circulation measurements and this gave, for typical modes of vortex shedding, time histories over an average cycle. The transverse force and the circulation tend to fluctuate in sympathy with each other, except around the instant of flow reversal when the force changes sign but the circulation remains high. Values of the strength of shed vortices, estimated from the measured circulation, are found to be comparable with steady-flow results. For KC [lsim ] 30, modes of vortex shedding occur over distinct ranges of KC with spanwise correlation high at the centre of a KC-range for a particular mode of shedding but low at the boundaries. Above KC ≈ 30 the correlation is no longer very sensitive to KC and the correlation length is estimated to be equal to 4.65 cylinder diameters. In the transverse vortex-street regime (8 [lsim ] KC [lsim ] 15) the cylinder was found to experience a steady transverse force, the coefficient of which is estimated to be about 0.5 at KC = 14.

Ground-penetrating radar antenna orientation effects on temperate mountain glaciers

Geophysics ◽  
2017 ◽  
Vol 82 (3) ◽  
pp. H15-H24 ◽  
Author(s):  
Lisbeth Langhammer ◽  
Lasse Rabenstein ◽  
Andreas Bauder ◽  
Hansruedi Maurer
Keyword(s):  
Ground Penetrating Radar ◽  
Flow Direction ◽  
Order Effect ◽  
Single Pair ◽  
Dipole Antennas ◽  
3D Numerical Modeling ◽  
Dipole Orientation ◽  
Bedrock Topography ◽  
Glacier Flow ◽  
Ground Penetrating

Ground-penetrating radar (GPR) surveys on glaciers are generally restricted to a single pair of bistatic dipole antennas orientated either parallel or perpendicular to the surveying direction. Extensive helicopter-borne and ground-based GPR investigations on the Glacier d’Otemma, Switzerland, demonstrated that the detectability of the ice-bedrock interface varies substantially with dipole orientation. We recorded several across and along profiles using two different commercial GPR systems operated with 15, 25, 50, and 70 MHz antennas. Dipole alignments parallel to the glacier flow generated considerably stronger and more coherent bedrock reflections compared with a perpendicular dipole setup. We observed the behavior for all the systems and antenna frequencies that we used. To help explain these findings, we performed 3D numerical modeling using the open source software gprMax. Simulations with 20 MHz transmitting and receiving dipoles indicated that the changes of the bedrock reflection amplitude are primarily governed by the bedrock topography. Scattering and intrinsic attenuation may also influence the amplitudes of the bedrock reflections, but these effects seem to be much less pronounced. Evidently, to increase the GPR bedrock reflection quality, dipole antennas should be orientated parallel to the glacier flow direction on a glacier confined to a valley. Because the directional dependence is a first-order effect, it is advisable to perform multicomponent surveys when the general shape of the bedrock topography is unknown. The multicomponent setup preferably consists of two sets of dipole antennas, each in broadside configuration and the sets being orthogonal to each other.

scholarly journals Influence of Heat Transfer on MHD Oscillatory Flow for Eyring-Powell Fluid through a Porous Medium with Varying Temperature and Concentration

2020 ◽  
pp. 3355-3365
Author(s):  
Dheia Gaze Salih Al –Khafajy ◽  
Lqaa Tareq Hadi
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Perturbation Method ◽  
Couette Flow ◽  
Poiseuille Flow ◽  
Oscillatory Flow ◽  
Fluid Motion ◽  
Oscillating Flow ◽  
Influence Of Temperature

The aim of this research is to study the effect of heat transfer on the oscillating flow of the hydrodynamics magnetizing Eyring-Powell fluid through a porous medium under the influence of temperature and concentration for two types of engineering conditions "Poiseuille flow and Couette flow". We used the perturbation method to obtain a clear formula for fluid motion. The results obtained are illustrated by graphs.

Sign in / Sign up

Export Citation Format

Share Document